After I accidentally formatted my external hard drive, I tried to recover my files. It seemed to work perfectly using the lost partition function since I had not overwritten anything yet. The estimated size of the files I selected for recovery was about 182GB, but after having finished the procedure it said only about 90GB had been recovered with 5 files missing. They do not sum up to the 92GB difference, though, so I am wondering where all the data has gone. Partially, it might have to do with this: When opening some of the deleted video files, mostly .mov, I could only play to about 1:00-1:30 before the image stuck. The video itself kept playing, but with frozen image and without sound. Is there any way I can recover those videos properly or is this a sign of the files being irreversibly corrupted?

The size of the data after scanning provides an estimation of what this data may be after the recovery. The actual recovery (like the actual preview) is the only way to know how much data is recoverable. A lot depends on how fragmented the recoverable files are. The actual recovery might not find all the chunks of the missing files. You can find more info about the corrupted files after the recovery in our knowledgebase: /help/troubleshooting-scan-results/